The invention relates to the problem of fuel injection in a multiple-cylinder two-cycle engine, and in particular to the economic and reliable electronic control of such injection, particularly for engines having four or more cylinders.
To provide fuel injection in a two-cycle engine of the character indicated, it has been proposed to employ for each cylinder a solenoid-operated injector valve adjacent an injection nozzle, and to make the injection in the intake or plenum passage supplying inlet air and fuel via the check-valve vanes (or reed bank) which retain air and fuel admitted to the crankcase region of the particular cylinder. But this approach imposes severe timing and precision limitations on the injection portion of the cycle; for example, the injection period must be short, to assure that all or substantially all injected fuel can be admitted to the crankcase before the flow rate of induction into the crankcase approaches zero. The penalty for failure to admit all fuel to the crankcase is, in the case of an outboard motor wherein cylinders are in vertically stacked array, to allow unduly enriched fuel-air mixtures in the lower cylinders, meaning inefficiency and failure to achieve design engine output, through an inability to deliver the same fuel-air ratio to all cylinders. Such limitations apply regardless of the sophistication that may be built into individual electronic timing circuits serving the individual fuel injectors.